STAURASTRUM. 149 



SCOTLAND. Sutherland, Ross, Aberdeen, Kincardine, 

 Forfar !, Perth !, Dumbarton, Argyle and Renfrew (Roy 

 & Biss.). Xorth of Fort Augustus, Inverness ! 



IRELAND. Carrantuohill, Kerry ! Slieve Donard, 

 Down (at 2000 feet) ! 



Geogr. Distribution. Germany. Sweden. C4reenland. 

 Azores. 



This variety differs from the type chiefly in its broader semi- 

 cells and rather longer processes, and in the greater development 

 of the verruca. 



f 



143. Staurastrum natator West. 

 (PL CXLVII, fig. 7.) 



Staurastrum natator West, Aljr. W. Ireland, 1892, p. 183, t. 23, f. 14 ; West 

 & G. S. West, Brit. Fresh\\ . I'liyt<. plankton, 11*09, p. 202. 



Cells of medium size, about twice as long as broad, 

 excluding the processes, constriction fairly deep, sinus 

 small, acute, semicells subquadrangular, broadening 

 slightly upwards, lateral margins slightly crenate, apex 

 with three large mucronate or emarginate verrucse, 

 upper angles produced to form long diverging processes, 

 tipped with 3 minute spines and with many series of 

 denticulations, centre of each face with a rounded pro- 

 tuberance ornamented with about 7 or 8 granules 

 arranged in a circle. Vertical view rounded or rhom- 

 boidal, elongated at the poles to form long processes, with 

 a prominent subtruncate protuberance in the middle of 

 each lateral margin, and 2 series of 3 verrucae on the 

 apex. Semicells in side view rounded, with a protuber- 

 ance on each side, and a process projecting vertically 

 between two apical verrucao. 



Zygospore unknown. 



Length, without processes, 34-38*5 \L ; with processes, 

 53-67 pi ; breadth at base of semicell 15-20 pi ; at apex, 

 excluding the processes, 20-25 pi ; breadth, including 

 processes, 57-75 pi ; length of processes 20-32'5 pi ; 

 breadth of isthmus 8-1 2 '5 pi ; thickness 19-2 1*5 pi. 



SCOTLAND.- -Rhiconich, Sutherland ! 



